Tool for grinding both fields of bifocal lenses simultaneously.



0. 0. KRIEGH. TOOL FOR. GRINDING BOTH FIELDS 0F BIFOOAL LENSES SIMULTANEOUSLY.

APPLICATION FILED JUNE 16, 1911.

31,015,030. Patented Jan. 16, 1912.

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.. UNITED STATES cHl 1 :cIE 0. arma, or ossmn, INDIANA.

Fields'cf'Bifocal Lenses Simultaneously, of

TOOL roa GRINDING BOTH. means or BIrocAL LENSES smumnnaousrv.

To all whom it my concemi Be it known that I, .CHANOIE C. .IKRIEGH,

a citizen of the United States, residing at .Ossian, in the county of Wells and State of Indiana, have invented newand useful Improvements in Tools for Grinding Both which the following is a specification.

- This invention relates to tools for 'grinding'lenses for spectacles, eye glasses and the like,in which lenses -two fields of different- .radii are provided.

. The object of my invention is to provide a simple and efficient tool having a grindingsurface interrupted by a second grinding surface, the latterbeing removable so that a grinding surface having a different radii maybe substituted in its stead, thereby enabling the former grinding surface to be used in combination with any one of a large number of interrupting "grinding surfaces of different radii.

, as desired, and it is designed to My invention consists in the novel construction, combination and arrangement of parts hereinafter described, of which one exemplification 'is illustrated in the drawings, in whi'ch- Figure l is a top planview of a grinding tool provided with my invention; Fig.9, a central vertical section of Fig. 1; Fig. 3, a top plan view of the tool with the removable grinding member removed; Fig. 4, a central vertical section of 3; Fig. 5, a top plan view of a removable grinding member and Fig. 6, a central vertical section of Fig. 5.

Referring to the drawings, 1 is a spindle by which the head ordisk D is secured to a rotatable support, not shown. The top or grinding surface of the disk is given the desired curvature-as the concave surface 2.

This surface may have any desired radius of curvature and may be concave or convex grind the upper or far field of the lens. ThlS surface 2 is interrupted by an annular concentric recess or channel 3. in disk D, the side walls of which may be parallel or tapered as- Openings 4 lead'from the bottom shown. surface of the disk into qhannel 3. In channel 3 is snugly fit a ring 5, the top surface 6 of'which is fiat orconcave or convex of anydesired radius of curvature, and it is designed'to grind thei 'lower or near field of the lens. The outer and inner top edges of the ring coincide accurately with the adja'cent edges of the disk D so as to obvlate Specification of Letters Patent. Patented Jan. 16, 1912- Application filed June 16, 1911*. Serial No..638,586. i

a sharp line of demarcation between the two "fields of the lens when produced by surfaces 2 andG. Ring 5 is preferably provided with threaded openings 7 in its lower surface which may be brought into register with openings 4 in disk D through which registeri'ng openings bolts or screws 8 are inserted for securing ring 5 to the disk. The contacting tapered sides of ring 5 and channel 4 furnish suflicient friction to securely retain the ring in the channel, but I prefer-to use bolts or screws-'8 as securing means for the purpose. Openings 4 also serve to adrinigi a tool for dislodging a ring 5 from the It is apparent that any number of rings .5 may ,be provided each of which will have a top or grinding surface of a curvature difffering in radius from any of the others so that with a single tool with a selected radius ofcurvature for surface 2 a ring 5 having the desired radius of curvature for its grinding'surface may be combined, thereby enabling the operator to grind bifocal lenses in many combinationsof fields and avoiding the necessity of constructing a complete tool for eachof those combinations. All that the operator has to do isto select the disk and ring havingthe desired radii of curvature, assemble them and grind the lens. For another combination he may use-the same disk with another ring or the same ring with an other disk. In case the grinding surface of the ring, or any ring, becomes worn down so that it does not properly register with,

the disk I may insert a bushing. or shim between theliottom of the ring and the bottom of the channel thereby elevating the ring to the proper height, the screws being of suflicient length to'permitof this adjustment.

It will be understood that in the operation of grinding lenses-with the tool above described it will be necessary that the lens be made to rotate about a transverse axis independently of the rotation of the tool and that the lens shall be placed in a fixed position relative to the disk in order that the fieldsshall be made on the lens. Means for accomplishing these conditions are well known in theart and as they formno part of my present invention I do not illustrate them.

What I claim is: 'A tool for grindinggfthe fields of bifocal lenses simultaneously comprising a head having a grinding surface thereon, an annular" channel in the head interrupting the 'said openings and engaging the ring'for recontinuity of the said surface, openings in mo'vao ly securing the ring in the channel. 10 the head extending from the bottom of the 1h Witness whereof, I hereunto subscribe -channel t0 the tear or lower side of the my name this 12th day-0:" June, 1911.

5 head, a ring in the channel having a gri'nd- CHANCIE C; KRIEGH.

ing surface, the curvature of Whlch differs 1 Witnesses: from that of the curvature of the grinding IIELEN F. GLENN, surface of thehead, and rotatable means in E. M. HULsE.

M Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

